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About The Author

Robert A. Burton, M.D.Robert A. Burton, M.D.

Robert Burton, MD is a physician, journalist, and author. A graduate of Yale University and University of California at San Francisco medical school, he was formerly chief of the Division of Neurology at Mt. Zion-UCSF Hospital and Associate Chief of the Department of... More

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1 • The Shape of Your Mind
It’s unbelievable how much you don’t know about the game you’ve been playing all your life.
—attributed to Branch Rickey1
All complex biological systems—which include you and me—use sensory feedback to monitor their environment. We are made aware of the external world through senses such as sight and sound; we know our interior physical world through internally generated feelings such as hunger and thirst. As the vast majority of thought originates outside of consciousness, it seems reasonable that we would also have evolved a sensory system for informing the conscious mind what cognitive activity is going on subconsciously. Without a method for being aware of this activity, it is hard to imagine what role the conscious mind would have, or even if there would be such a thing as a mind.
If we were cars, our minds would have LED displays telling us what is going on under the hood. But being subtle creatures rather than machines, we have a far more sophisticated system for monitoring subliminal brain activity. Instead of a mental dashboard full of flashing lights, we have evolved an array of cognitive feelings. For simplicity, I’ve used the phrase “cognitive feelings” to refer to those mental phenomena that aren’t normally categorized as emotions or moods, but rather are the type of feeling we associate with thinking. These include such diverse mental states as a sense of knowing, causation, agency, and intention.
To be meaningful, these feelings must bear some relationship to the cognitive activity they are announcing. Just as the feeling of thirst must trigger the desire for drinking fluids, an awareness of a subliminal mental calculation must feel something like a calculation. And here’s the rub. Thirst and hunger are readily accepted as arising from our bodies, but feelings about our involuntarily generated subconscious thoughts often feel like deliberate actions of the conscious mind.
Take an example from the world of visual perception. Imagine yourself at a local football game. You are focused on the game and oblivious of the surrounding faces of spectators. Then, while you are shifting your gaze to look at the scoreboard, your visual system subliminally detects a face in the crowd that it recognizes as your old friend Sam. Your visual cortex compares the incoming image of the face with previously stored memories of Sam’s face and calculates the probability that the face is Sam’s. If the likelihood is high enough, the brain sends the image of the face up into consciousness along with a separate feeling of recognition. You feel as though you consciously assessed the face and determined it was Sam. Depending upon the strength of this feeling of recognition, you will also sense the degree of likelihood that this facial recognition is correct. This might range from a feeling of merely “maybe” or “it could be, but on the other hand…” to a sense of utter certainty.
A visual input of a face, though not initially making any conscious impression, has triggered two separate unconscious brain activities. One is exclusively mechanical and without any associated feeling tone—the comparison of Sam’s face with all other faces previously stored in memory. The other is purely subjective sensation—the feeling of recognition. The two arrive in consciousness as a unit—the visual perception of Sam’s face and the simultaneous feeling that it is indeed Sam. Even though this process occurs outside of awareness, we feel it is the result of the act of conscious recognition. Such lower-level brain activities are experienced at a higher level as voluntary acts.
Because we know the brain is superb at subliminal pattern recognition, we find it relatively easy to concede that recognition doesn’t take place consciously, despite how it might feel. But there are a host of mental sensations that are so intimately linked with our conception of conscious thought that the idea of them not being under our conscious control seems far-fetched.
In my previous book, On Being Certain, I introduced the concept of involuntary mental sensations—spontaneously occurring feelings about our thoughts that are experienced as aspects of conscious thought. Though we feel that they are the result of conscious rumination and represent rational conclusions, they are no more deliberate than feelings of love or anger. My focus was on feelings of knowing, certainty, and conviction—feelings about the quality of our thoughts that range from vague hunches and gut feelings to utter conviction and a profound “aha.”
I now realize that feelings of knowing are a small part of a larger mental sensory system that includes the sense of self, the sense of choice, control over one’s thoughts and actions, feelings of justice and fairness, and even how we determine causation. Collectively, these involuntary sensations make up much of the experience of having a mind. In addition, they profoundly influence how we conceptualize what a mind “is.”
It is vitally important to realize that the cognitive aspect of thought—the calculation—has no feeling tone. Our entire experience of these calculations comes via separate feelings that accompany them into consciousness. For example, though contrary to personal experience, there is no way to objectively determine the origin of a thought. When an idea “occurs to me” or feels as though it “popped into my head,” I tend to label it as arising from the unconscious. On the other hand, if I have the feeling of directly thinking a thought, I am likely to conclude that it is the result of conscious deliberation. The distinction between conscious and unconscious thought is nothing more than our experience of involuntary mental sensations.
This separation between thought (the silent mental calculation) and feelings about thoughts is central to any inquiry into what the mind might be. We know the mind only through our experience; it isn’t something that can be pinned on a specimen board, weighed or measured, poked or prodded. Seeing how our sense of a mind arises from the messy and often hard-to-describe interaction of disparate involuntary sensations is a necessary first step toward any understanding of what the mind can say about itself.
Our Brains, Ourselves
A car cuts you off on the freeway and you get enraged; you honk, flip the driver the finger, fume, and carry on about this brutish lack of manners being a surefire indication of civilization’s impending demise. Your spouse, for the thousandth time, urges you to learn a little self-control. Of course, dear, you halfheartedly agree, your mind oscillating between further thoughts of revenge and the painful recognition that you have just acted like a two-year-old.
You quickly drum up a bevy of seemingly reasonable explanations—a stressful day, a poor night’s sleep, the new anti-hypertensive medication you started a couple weeks ago, long-standing control issues and unresolved childhood slights, your growing apprehension over your declining IRA account. On the other hand, your father had a hair trigger and was prone to seemingly unprovoked tirades and furies. Perhaps you inherited some angry strands of tightly wound DNA. If only there was a straightforward method for self-examination. But your mind reels at the seemingly infinite combination of possibilities, as though the very concept of self-awareness is an overrated myth, a low-probability rubber crutch for the emotionally desperate.
Nevertheless, you have to start somewhere. Though changing your genes is presently out of the question, perhaps you can address your financial concerns. Back at home, you review your IRA portfolio. Your best friend, a financial wizard, gives you a thousand reasons why stock prices are at a generational low and insists that you should “buy, buy, buy.” His arguments are persuasive. You boot up your online broker and poise your finger over the Buy button; but, as though controlled by invisible forces, you have a complete “change of heart” and sell everything. You are puzzled by your behavior. It is as though you have lost control of yourself.
Later that night, flipping through a popular psychology magazine, you read that fMRI studies have shown that the brain region for controlling hand movements is activated before you are aware of making a decision to move your hand. Brain wave (EEG) studies confirm the finding. This can’t be, you think. You try a simple lab experiment. You think about moving your hand but don’t make the final decision to move it; your hand rests quietly in your lap, awaiting instructions. You then consciously decide to wiggle your fingers. You exert some effort, and, not surprisingly, your fingers wiggle on command.
But if the fMRI and EEG studies are correct, your experience of wiggling your fingers voluntarily is nothing more than a comforting illusion foisted on you by an unconscious with its own agenda. Only after the fact did your subconscious let “you” know what it had already decided and acted upon. Looking down at your hand as though it has a mind of its own, you wonder who exactly made the decision. “Who am I?” you ask yourself, at the same time wondering who is doing the asking and who is expected to answer.
To come up with anything remotely resembling a tentative answer to what the mind might be and do, we first need some working understanding of the placeholder for the mind—the self. A mind isn’t an impersonal organ like a liver or a spleen; it is an integral aspect of a self, a part of what makes us an individual as opposed to an object. It’s the center of our being, the main control panel for our thoughts and actions. The self’s central function—creating thoughts and actions—is commonly what we mean when we talk of a mind. Evolution isn’t a linguist. At a practical level, the mind and the self are inseparable. It is hard to imagine a functional self without a mind, and vice versa. Both are essential constituents of an “I.” When a patient with Alzheimer’s disease “loses his mind,” he is invariably described as having also lost his “selfhood.” Though we can readily create thought experiments about a brain in a vat, we cannot even begin to think of a mind in a jar. The mind needs to be physically embodied; there needs to be a something or someone that is having the thoughts and performing the actions. Fortunately, we have a built-in set of mechanisms for creating a visceral sense of a home for the mind—the physical self.
Where Am I?
Perhaps the most universal yet personal of all involuntary mental sensations is the feeling of where “you” exist in your body. Many of us have a very strong sense that the center of our being is a few inches behind our foreheads, just above our eyes. But, if we could take off the top of our skull and closely dissect each of our brains down to the subatomic level, we would find no homunculus, no little “I” running the ship, minding the store, holding the reins of our conscious actions, or even idly ruminating. The center of our being is nowhere to be found.
At the purely intellectual level, even the most science-impaired among us understand that mental states, no matter how seemingly psychological in origin, ultimately arise out of brain states. Everything we experience is generated by mindless brain cells and synapses. Nevertheless, we cannot shake the contrary feeling that there is a personal “I” that is sufficiently separate from these states to have an understanding of this proposition. As I write this statement, I have the undeniable feeling that there is a special “I” that is both writing and reading this sentence, and that this “I” resides within a larger unit over which I claim at least some degree of responsibility—my personal body.
It is impossible to imagine what it would feel like to lack a consistent sense of self. We couldn’t take complex actions, consider “what might have happened” in the past, contemplate a future, or make plans.2 Yes, it would be wonderful if we could occasionally flip a switch that would free us from the downside burden of perpetual self-involvement and internal dialogue, but that’s not the way the physical sense of self works. It is as involuntary as hunger and thirst.
For now, put aside considerations of personal aspects of a self—the narrative of your life that you tell yourself and others. I want to focus on the more basic physical sensations that collectively create the scaffolding of a self onto which you hang your personal memories, stories, and experiences, for it is this physical sense of self that creates the housing for our experience of a mind. We don’t experience our mind as being several blocks away in a saloon, nursing a drink while contemplating the universe. For most of us, most of the time, the mind resides within our personal sense of the dimensions of our self.
The spatial qualities of the experience of a mind arise from subconscious brain mechanisms. Our thoughts about the dimensions of mind aren’t similarly constrained by our biology. Conceptually, the mind can be anything that we imagine. This distinction between felt experience and theoretical views of a mind is critical to any larger understanding of what a mind “is.” To lay the groundwork, we first need to know how our experience of the dimensions of our minds shapes our investigation of our minds.
A basic tenet of neurological research is to break down a complex mental state into more manageable subcomponents. One method—studying patients who have had a discreet brain insult that clinically affects only one of these subcomponents—has been instrumental in providing a good practical model of how sensory systems work. For example, this technique has helped reveal that the visual system is composed of a number of specialized neural circuits (modules); each processes an aspect of vision such as lines, edges, color, or motion. Collectively they create a visual image. We will use this same approach to dissect out the various mental sensations that collectively create a sense of self.
To begin, listen to these three descriptions of how abnormal electrical brain activity can dramatically alter our sense of self. As you read these histories, notice how the physical sense of self can be distinguished from the felt location of your particular first-person vantage point in the world.
Patient #1
A twenty-one-year-old man with a six-year history of poorly controlled seizures awakened with a peculiar dizzy feeling. He got out of bed but, when turning around, saw himself still lying in bed. He became angry about “this guy who I knew was myself and who would not get up and thus risk being late at work.” He tried to wake the sleeping body by shouting at it, then by trying to shake it and then repeatedly jumping on his “alter ego in the bed.” The body didn’t respond. Puzzled about his apparent double existence, the patient became frightened by his inability to tell which of the two he really was. Several times his bodily awareness switched from the one standing upright to the one lying in the bed. While in the lying-in-bed mode he felt quite awake but completely paralyzed and scared by the figure of himself bending over and beating him. He walked to his bedroom window, looked back to see his body still in bed. “In order to stop the intolerable feeling of being divided in two,” he jumped out the third-story window.
Fortunately, he landed in a bush and sustained only cuts and bruises. Neurological evaluation documented recurrent seizure activity triggered by a slow-growing tumor in the man’s left temporal lobe. The tumor was successfully removed.3
Patient #2
A fifty-five-year-old man with a history of seizures from age fourteen developed recurring stereotypical attacks of strange bodily sensations. Without warning he would feel that a stranger had invaded the left side of his body and that the left half of his head, the upper part of his left trunk, and his left arm and leg no longer belonged to him. During an episode, he felt that he existed only in the right side of his body, yet he was able to carry on normal activities, including giving lectures.
Fiction is filled with fascinating tales of the doppelgänger. In Edgar Allan Poe’s “William Wilson,” the protagonist, in an attempt to stab his double, kills himself. In Oscar Wilde’s The Picture of Dorian Gray, the hero commits suicide in order to escape the horror of being haunted by his second self. When reading such stories we readily suspend disbelief; we understand that they are intended as metaphors rather than realistic accounts. Though the above case history also feels fictitious, it is a very real description of a relatively rare neurological phenomenon—autoscopy—seen with certain types of paroxysmal brain activity (i.e., seizure disorders and migraine). This experience of a transiently divided and unstable sense of self provides an excellent starting point into how the physical self is generated.
Patient #3
A thirty-year-old man had a twenty-year history of seizures characterized by an overwhelming sense of numbness in his legs, chest, and neck. During the attacks he would lose awareness of everything below his chin so that his head felt detached from the rest of his body. He simultaneously experienced himself as an observer of his body and the subject of observation.4
In the first example, patient #1 feels and knows that he is standing by the bed, yet continues to have the unshakable feeling that the illusory body in bed belongs to him. This sense of ownership—sometimes referred to as a feeling of “mineness”—is thought by many cognitive scientists to be central to self-awareness. Take a look at your hands. Though you have no doubt that these hands are yours, this determination doesn’t require any conscious deliberation. This feeling of ownership is pure sensation, no different from feeling the weight of the book that you’re presently holding in your hand. Visual and proprioceptive inputs inform us about the position of our body parts; touch inputs tell us what our body is in contact with. This information is converted into a coordinated body schema—a representational map of the body and its relationship to the outside world that is experienced as “mine.”
Imagine our perpetual confusion if we had to first distinguish what is “us” from what constitutes our surroundings, or even worse, who is “me” and who is “another.” If you saw a hand rapidly approaching your face, you wouldn’t be immediately able to know if you were about to unconsciously scratch an itch or were getting mugged. Mercifully, evolution has given us a built-in method for immediate recognition of our body and its parts. This sense of physical self not only allows us to move through the real world; it also enables us to navigate the world of our imagination—both alternative pasts such as what might have happened “if only…” and projected scenarios for the future. Onto this most basic map of the dimensions of “me” we hang our nonphysical self—our collected thoughts and memories.5
The feeling of ownership is dependent upon unconscious mechanisms telling us that the current body image closely approximates previously stored body imagery.6 Patient #2 provides us with a dramatic picture of how this sense of ownership of body parts can be temporarily switched off during a seizure. This loss of sense of ownership of one side of the body is commonly seen in patients with lesions in a region of the right parietal lobe believed to be instrumental in the generation of our body schema. Patients characteristically comment that the affected side of the body no longer feels “theirs”; they will often attribute ownership to an outside force. I still remember Mrs. A, an elderly deacon in her Pentecostal church, who, after a stroke in the right parietal region, claimed that the left side of her body belonged to the devil. She repeatedly grabbed her paralyzed left arm with her right hand and tried to throw it out of bed. No amount of explanation reassured her that her arm was “hers.”
(A word of caution: though denial of body parts is most commonly associated with right parietal lesions, premotor regions of the frontal lobe also have been implicated in the sensation of a sense of self, including recognition of body parts. However, the final word as to the underlying neuroanatomy isn’t in.7 The purpose of this discussion is to point out the involuntary neural basis of such mental states, not to take a stand on the underlying neuroanatomy, as this may well be modified with further studies.)8
A second feature common to patients #1 and #3 is an altered sense of where “I” exists. Patient #1 describes a sense of “I” that rapidly shifts back and forth between the two bodies. Patient #3 describes the equivalent of a mental double vision in which he is simultaneously observing and being observed. These descriptions of a short circuit–induced sense of “I” separate from a sense of the physical body underscore its origin in brain wiring.
This dissociation between the felt location of “I” and where your body is physically located is the hallmark description of an out-of-body experience (OBE). Swiss neuroscientist Olaf Blanke and colleagues have shown that an OBE can be directly provoked with seizure activity, brain stimulation, and certain psychoactive chemicals.9 Patients typically describe floating or hovering above their own bodies, perhaps watching a surgical procedure or even witnessing their own death. Despite the innumerable fanciful explanations, OBEs are nothing more than illusions generated by quirks of physiology.10
The investigation of such perceptual illusions has provided some remarkable insights into how easily our sense of self can be physically manipulated. Perhaps the most generally known is a simple parlor trick—the rubber hand illusion. A test subject is seated at a desk, with one hand placed under the desk so that it is hidden from view. On the desk in front of him is an artificial rubber hand. The subject is asked to focus his attention on the rubber hand. When the experimenter simultaneously strokes the hidden and rubber hands with a paintbrush, the visual information—seeing the rubber hand being stroked—overrides the subject’s proprioceptive knowledge of the position of his hidden hand. Within a minute or two, the subject perceives the rubber hand as his own.11
More recently, the studies have been extended to include the entire body—the body swap illusion. By altering the perspective with which subjects see themselves, the sense of ownership can be transferred to a mannequin or even another person. The trick is to create a visual image of the subject’s body that is different from our customary experience of looking down at our bodies from the perspective of our eyes. To do this, subjects are fitted with a head-mounted display—a modified virtual-reality headpiece connected to a video camera placed behind their backs. Seeing themselves from the camera’s point of view induces a form of OBE; the subjects describe their center of awareness as being located outside of their physical bodies.
After determining how the sense of location of the self can be readily manipulated by altering sensory inputs, two Swedish neuroscientists have devised several fiendishly clever experiments.12 In one study, they make subjects feel a sense of ownership of a mannequin standing alongside them. Even though the subjects can clearly see that the mannequin is not them, the subjects cannot shake the feeling that their sense of self is located inside the mannequin. The extent of this altered sense of self can be seen when the mannequin is approached with a knife. Subjects display increased sweating and increased skin conductance response, and may describe feeling anxious. Changing their sensory inputs makes the subjects emotionally identify with an illusion.13
The evidence is overwhelming: the most basic aspects of a sense of self—its physical dimensions and where we experience our center of awareness—are constructed from sensory perceptions. It is hard to avoid the comparison with a virtual avatar. Both are pure constructs that nevertheless generate a real sense of personal identity. And, just as the height, weight, or dimensions of an online avatar can be changed, the dimensions of a self are also subject to change. Consider the following monkey-rake experiment.
In the 1990s, using microelectrode recordings, cognitive neurobiologist Atsushi Iriki located neurons in the parietal region of monkeys that respond to both visual and touch input.14 These cells fire when an object is placed near the monkey’s hand, as though announcing the presence of an object within the monkey’s reach. The monkeys are then taught to use a rake to extend their reach. Soon the same cells fire whenever the monkey sees anything within reach of the rake. The rake has been incorporated into the neural representation of the monkey’s body schema as an extension of its arm and hand.15
The speed with which this change in body image mapping occurs is quite impressive. Macaque monkeys rarely use tools in the wild but can become proficient in tool usage with a few weeks of training. Within a week of beginning training, fMRI scans will show increased volume of gray matter in the same regions that exhibit increased neuronal firing rates.16 Though the exact structural explanation for this increase in brain volume remains unclear, it is thought that this may represent either new blood vessel formation in the region or even possibly the generation of new brain cells (neurogenesis).17
Whatever the underlying anatomic explanation, it is clear that the brains of these monkeys can easily be rewired by the use of tools. The same seems likely to apply to us. In 2009, fMRI studies showed similar areas of brain activation when volunteers were exposed to new tools.18 Though I am generally suspicious of pat evolutionary explanations for all physical adaptations, it is hard to avoid the conclusion that evolution has provided us with a certain innate flexibility of body image that has allowed us to acquire the skillful use of tools. But this mutability of our representational maps of our body extends beyond tools.
Seventy-three-year-old Mrs. B sustained a large right hemisphere stroke resulting in left arm paralysis. She remained cognitively intact with no signs of confusion, yet demonstrated a total lack of awareness and sense of ownership of her paralyzed left arm, repeatedly claiming that the arm belonged to someone else. Surprisingly, this lack of any feeling of ownership included her wedding rings, which she wore on her left hand. Though she was able to clearly see and describe the rings, she denied that they belonged to her. When the rings were shifted to her right hand and then shown to her, she immediately felt they were hers. To see if this loss of ownership extended to other objects not normally associated with her left hand, a comb and a set of keys were placed in her paralyzed hand. Both were recognized immediately as “my comb” and “my key-holder.” The lack of ownership was sharply circumscribed, limited to that set of objects—her wedding rings—that were historically related to her sense of her left hand. It was as if, before the stroke, the rings had been included in an extended, primarily visual body schema.19
Pundits are quick to point out that web surfing, video games, online virtual environments, Twitter, Facebook, and innumerable other technological innovations are changing our brain circuitry. The notion of an extended mind has become commonplace, with the monkey-rake experiment frequently being offered as hard evidence for how these changes take place. Yet even as we acknowledge the profound effects of our environment on our brain, most of us continue to feel that we possess our own individual minds that are at least partially immune from insidious outside influences. It is hard to overcome the basic sense that a mind is embodied within the confines of a self—the essential distinction between the experience of a mind and the concept of a mind.
I recently heard an eminent philosopher and logician, the University of California, Berkeley, professor John Searle, say, “The extended mind ought to seem mistaken on the face of it.… In general, in philosophy, if you get a crazy result, it’s false.… If someone gives you an account of the mind that runs counter to your own experience, well then, you know they made a mistake.”20 Searle is well aware that all experience is subjective perception, and all perception is filtered through undetectable biases and predispositions. Personal feelings shouldn’t be the sole measure of an idea. Nevertheless, Searle cannot step back from his own feeling that he possesses a unique mind (the sense of ownership) residing within his personal body (the sense of physical self) that has willfully drawn this reasonable conclusion (sense of agency). This combination of involuntary mental sensations restricts his ability to entertain alternative possibilities for what a mind might be—a poignant reminder of how philosophical conclusions can be guided by biology rather than by reason.
The description of Mrs. B provides a Rube Goldberg–like insight into how this conflation between the sense of a self and a mind might affect the very experience of our thoughts. (For the purpose of this discussion, I am separating the mind from a sense of self, though obviously there is a significant degree of overlap and neither seems capable of an independent existence.) Over time Mrs. B’s sense of ownership of a body part (her hand) came to include the body part’s contents (her rings). As the mind is a lifelong key component of the self, a sense of ownership of the self similarly is likely to extend to its contents—the mind. In turn, as our thoughts are a central component of our mind, we might expect some overflow of this sense of ownership from the mind to its contents—our thoughts. Each of us possesses “my mind” and “my thoughts.”
As we explore the role of mental sensations in creating the structure of the self, try to get a sense of how you know when a thought is “yours.” Whether this feeling of having your own thoughts is a willful determination or an involuntary mental sensation is critical to how we determine what a mind “does.”
Moat Around the Castle
Before leaving the subject of the physical dimensions of a self, we should take a quick look at a separate but closely allied phenomenon—the sense of a personal space. Each of us has his own preferred distance between himself and others. Move closer and you’re “invading my space.” If the physical sense of self is the brain’s version of a car’s Global Positioning System (GPS), which tells you where the car is in relationship with the environment, the sense of a personal space would be equivalent to a car’s sensors, which tell you when you are too close to another car or about to back into a telephone pole.
This sense of personal space can be dramatically altered with brain disorders.21 The most extensively studied example is S.M., a woman in her midforties with a rare genetic condition that has resulted in extensive bilateral damage to her amygdala.22 S.M. has a reputation for being fearless and superfriendly, with a tendency to “violate” what others perceive as their own personal space.23 During a series of trials exploring her sense of personal space, she admitted that she didn’t feel discomfort at any distance from the experimenter. On one occasion, she walked up to the experimenter until their noses were nearly touching. The experimenter was the only one who felt uncomfortable.24
A similar lack of need for a personal space is seen in another genetic condition—Williams syndrome. Though saddled with a number of developmental problems and learning disabilities, patients with Williams syndrome are highly social and friendly, and are typically unafraid of strangers.25 Like S.M., they apparently don’t feel the need for any significant degree of personal space; as caretakers will attest, they are commonly “in your face.”
Both S.M. and children with Williams syndrome exemplify the role of basic brain mechanisms in determining the size of the buffer zone with which we unconsciously surround our physical sense of self. I’m not suggesting that this feeling is exclusively shaped by our biology. For example, ethnic and cultural influences clearly make a difference. Those from the Middle East and southern Europe seem comfortable with less interpersonal space than northern Europeans.26 Whether a feeling arises exclusively out of innate biological factors, sociocultural influences, or any combination of nature and nurture, the final result will be expressed as a mental sensation.
That a sense of personal space is likely to be the product of separate brain mechanisms than the sense of a physical self should serve as a huge caveat. Though this and subsequent chapters are designed to show how a variety of cognitive feelings shape our sense of self, the list is by no means complete. I suspect that cognitive scientists and/or you readers will come up with suggestions for other potential candidates. Also, it is likely that these various sensations will be experienced and described differently. For example, I recently asked a group of psychoanalysts where they felt the central core of the “self” was located. Most opted for the head, while one senior clinician rubbed her upper abdomen. When I asked her why she picked her abdomen, she said with a wry smile, “Because that’s how I feel.” This discussion isn’t meant as a written-in-stone compendium of specific sensations so much as a way of understanding how the physical self is a pure projection of involuntary sensations.
A second problem to briefly consider: if the physical self is pure sensory projection, is it correct to call it an illusion? On the one hand, the physical sense of self is clearly an illusion in that there is no underlying entity to which the feeling refers. On the other hand, it is important to avoid thinking of illusion pejoratively—that somehow an illusion isn’t “real.” The sense of the self, even if we call it an illusion, is as real as pain, anguish, or love. (We will later address this problem of “real” versus imagined or psychological—a false dichotomy commonly seen in medical reporting.) Despite my ambivalence over the term, I have decided to go with “illusion” for quite practical reasons. First, understanding the nature of an illusion is critical to dealing with it. If I see a straight glass rod bending as it is immersed in a beaker of water, I can make appropriate adjustments in how I think about what I’m seeing. Second, it is possible that contemplating the illusory nature of the physical self can lead to constructive therapeutic options—ways of actually altering how we experience our physical self.
For instance, seeing the physical sense of self as an illusion provides a potentially enlightening perspective on some otherwise puzzling mental disorders. Several years ago, I watched with utter horror and disbelief a Discovery Channel documentary on patients who wished to have a perfectly functioning arm or leg amputated. First described in 1977, this condition, variously referred to as apotemnophilia or body integration identity disorder, has generally been thought to be due to deep-seated psychological forces. After all, anyone who wants a good arm or leg cut off must be crazy. But the case histories of many of these patients fail to show any hint of what the underlying reasons might be. Often there are no associated psychological quirks or symptoms, nor is there any prior psychiatric history. One sufferer describes being only four or five when he first became fascinated at the sight of an amputee. He recalls that by age seven he was standing by a bus and said to himself, “If I just stick my leg under the rear wheel of the bus, it will run over it and my leg will have to get cut off.”27
In 2009, behavioral neurologist V. S. Ramachandran and colleagues studied four men with this disorder. Using a form of functional imaging, magnetoencephalography, they were able to detect a striking reduction (compared to normal controls) of electrical activity in the right superior parietal lobule when the affected limb was touched.28 The area of decreased activity corresponded to the area that was affected in Mrs. A, who thought her arm was the devil and was preoccupied with throwing it out of her bed.
Ramachandran has postulated that there is a primary neurological malfunction in this region of the right parietal lobe that coordinates incoming visual, sensory, and motor inputs to produce a dynamic body image. Knowing that this circuitry is defective doesn’t tell us the cause of this defect, but it does offer yet another view on how some mental conditions might arise from a disturbed physical sense of self. It also raises the possibility of new ways of contemplating therapeutic interventions.
Using the same principles underlying the rubber hand illusion, Ramachandran has developed the mirror box illusion to effectively reduce phantom limb discomfort in amputees.29 The principal is straightforward: you try to trick your brain into replacing the image of the missing part with an image of a perfectly functional normal extremity. If it’s an arm that’s amputated, the patient positions a mirror in his line of sight in such a way that when he looks at the missing arm, he sees only his good functioning arm. Various techniques such as gentle exercise or lightly stroking the hand augment this visual input. Functional imaging studies have shown that the brain undergoes reorganization of the image of the missing arm. The greater the degree of reorganization that occurs, the greater the degree of reduction in phantom limb pain.30
The same effect can be produced with a virtual environment in which an avatar’s hands are positioned so that the subject feels that the avatar’s hands are his own. By transferring the feeling of ownership to a virtual hand, recent amputees find it easier to adapt to a prosthetic limb. In effect, the patient’s brain is reprogrammed to accept the prosthetic limb as his own.31 Another example of the benefit of altering the body image is the use of lenses (inverted binoculars) to make a hand look smaller than normal. Patients with chronic hand pain who observed their affected hand as smaller had a significant reduction in their pain. Even more fascinating, these patients were noted to have measurably less movement-induced swelling. Conversely, when using binoculars to magnify the size of affected hand, the degree of reported pain and measurable swelling was increased.32
Intentionally altering a body’s representational maps could have far-reaching implications in a variety of disorders characterized by faulty body imagery—from anorexia nervosa to the body dysmorphic disorders that result in excessive plastic surgery (think of Michael Jackson or Joan Rivers).33 At the very least, such demonstrations highlight the intimate relationship between altered body imagery and how we see ourselves in the world—a perspective integral to scientific inquiry.
In summary, a sense of a coherent body image, where our center of awareness is located, and our first-person perspective on the world collectively establish the general frame of a self. We can even toss in the metaphor of a protective moat (sense of personal space) that surrounds this castle that is home to our personal kingdom. However you describe these feelings, what seems inescapable is that pure sensation is the sole necessary and sufficient prerequisite for the physical sense of a self onto which all of us, neuroscientists and philosophers included, hang our perceptions and generate our ideas of a mind.

Copyright © 2013 by Robert A. Burton, M.D.

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